Modern smartphone devices are typically equipped with location features. These devices may use signals from GPS satellites to identify a location, determine a direction of motion, and other navigation functions. However, in locations where the GPS satellite signals are weak, for example, when these devices are indoors, GPS may not function well or at all.
Some systems provide indoor navigation by using other information, such as wireless network signals, Bluetooth signals, compass data and accelerometer data as well as existing floor plans and pre-generated databases or indices of measurements. These models may be incomplete or inefficient, and may rely on dead reckoning calculations based on information from orientation devices to fill in any gaps. Thus, these systems make a guess, albeit a well-educated one, about where the user actually is based on where the user was estimated to be a short time ago. Because the error increases with each subsequent estimation, the accuracy of these estimations increases over time. Thus, after a short time, the estimated location of the user may be fairly inaccurate.
Some navigation systems, such as Google Maps for mobile, may allow users to indicate a problem with their location determination. For example, users may report inaccurate locations or even provide an actual location.